Method of preventing cold stalling and means therefor



March 17, 1959 o. E. LARSEN METHOD OF PREVENTING COLD STALLING AND MEANSTHEREFOR Filed April 18, 1956 INLET FOR HEATING FLUID TO PASSAGE 42OUTLET FOR HEATING FLUID FROM PASSAGE 42 IGNITION SWITCH ZNVENTOR. O. E.LAR S E N A TTORNEVS United States Patent METHOD OF PREVENTING COLDSTALLING AND MEANS THEREFOR Olaf E. Larsen, Bartlesville, 0kla.,assignor to Phillips Petroleum Company, a corporation of DelawareApplication April 18, 1956, Serial No. 579,031 10 Claims. (Cl. 123122)This invention relates to the operation of carburetorequipped internalcombustion engines. In one of its aspects this invention relates topreventing cold stalling of an internal fuel combustion,carburetor-equipped engine by heating the initial air bleed section orpassageway of the carburetor. In another of its aspects, this inventionrelates to an improved carburetor device comprising a heater meanslocated in or adjacent to the initial air bleed section or passageway ofthe carburetor.

It has been observed that an internal combustion engine, having acarburetor, will stall while being warmed up when certain combinationsof atmospheric temperature and humidity exist. This phenomenon has beenreferred to as cold stalling and has been thought to be caused by theformation of ice on the throttle plate and adjacent parts of thecarburetor, for example around the idling jet and throttle plate. Theice formation results from the cooling effect derived from thevaporization of fuels within the carburetor operative upon the moisturecontained in the air admitted to the carburetor.

, I have now discovered that cold stalling resulting from carburetoricing is mainly caused by ice which forms in the initial air bleedsection of the idle fuel system of the carburetor and not primarily bythe ice which forms on the throttle plate and around the idle ports, asheretofore believed. The present day carburetor usually consists of afloat chamber, a nozzle with metering orifice, a venturi, a throttlevalve, a choke valve, and a low speed or idle fuel system. The idle fuelsystem of a carburetor controls and delivers a rich fuel/ air mixture tothe induction system of the engine where it is mixed to the correctmixture ratio with air coming past the throttle plate. The idle fuelsystem also functions during light load operation so as to give a nearlyconstant fuel/ air mixture during the transition period between idlingand full operation of the high speed system. Maximum flow of fuel andair through the idle system ordinarily occurs between -35 miles perhour. The idle fuel system usually comprises an idle well, a low speedjet, an air bleed opening or openings, an idle air mixture needle valve,and port openings located near the throttle plate. The air bleed orbleeds, which are located above the idle well, serve two functions.First the air bleed serves as a syphon break to prevent the flow ofunmetered fuel. Second, the air supplied by the air bleeds, break up theliquid fuel mass so that pre-mixed. air and fuel are supplied to themanifold. When two air bleeds are present, there is usually arestriction in the idle passage between the bleeds which further helpsto break up the liquid fuel mass and to premix the fuel and air.

With reference to the construction of the carburetor and its operation,as just described, I have found that the flow of humid air into the idlefuel system of the carburetor will deliver to said system a quantity ofmoisture which, due to vaporization of fuel or gasoline which isoccurring at or near said opening or openings, will cause ice to form onthe surfaces of the idle passage, restrictions, and air bleed opening oropenings. This ice builds up rapidly and actually throttles or chokesoff the required flow of air-fuel mixture to maintain the engine atidling speed.

It is an object of'this-invention to provide an improved method ofoperating an internal combustion engine of the carburetor type. Itisanother object of this invention to'p'rovide an improved carburetorfor internal combus- ICC tion engines. A further object of thisinvention is to. provide an improved carburetor wherein cold stallingresulting from carburetor icing is eliminated or substantiallyminimized.

Other aspects, objects, as well as the several advantages of theinvention, are apparent from a study of this disclosure, the drawings,and the appended claims.

Cold stalling ordinarily is encountered whenever the weather conditions,in which the engine is used, are such as to provide a relatively highhumidity, for example above about 60 percent, and a temperature aboveabout 30 F. but below about 60 F. As noted, it has been commonlybelieved that cold stalling is caused by ice formation on the throttleplate and around the idle ports. Although ice does form on the throttleplate and around the idle ports of the carburetor, this is not nowthought to be the major or controlling factor in cold stalling ofengines. Thus, cold stalling still occurs to an appreciable degree evenwhen the throttle plate and idle ports are heated.

According to the present invention, cold stalling resulting fromcarburetor icing is eliminated or substantially minimized by heating theinitial air bleed or idle fuel system of a carburetor at a place atwhich the air bled. into the idle fuel system first'comes into contactwith idle fuel being admixed therewith.

Since the initial air bleed section is ordinarily positioned between anidle well and idle ports and is usually located in a top section of thecarburetor, it has been found that by placing a heater, for example anelectrical heater, in the vicinity of the idle air bleed section of thecarburetor, cold stalling is substantially reduced and in some cases isentirely eliminated.

In the drawing there is shown a conventional type carburetor as modifiedby application thereto of an electrical heater and a control circmuit,which will now be described.

Referring to the drawing, numeral 10 refers generally to a carburetorhaving a mixture conduit 11 with an air inlet opening 12 and outlet 13communicating with intake manifold 14. Air inlet 12 is controlled by achoke valve (not shown), which is rotatably journalled in the mixtureconduit wall structure. Outlet 13 is controlled by a throttle valve 17mounted on shaft 18, which is also rotatably journalled in the wallstructure of mixture con duit 11. Venturi stack 19 is formed on themixture conduit anterior to the throttle valve. A constant level fuelchamber 22 is provided for supplying fuel to main nozzle passage 23, 20through metering orifice 25, controlled by metering pin 27.

Fuel from fuel chamber 22 enters the idle well after passing through thehigh speed circuit metering rod jet 25. The fuel passes up throughpassage 28 and a calibrated restriction 29. After passing throughrestriction 29 the gasoline mixes with a stream of air coming in throughair bleed opening 30 (a small hole leading into the bore of thecarburetor). This tends to break up or partially atomize the gasoline.In addition, the idle bleed opening 30 is required in the system to actas a syphon break to prevent the flow of unmetered fuel. The gaso? lineand air mixture now passes through a small restriction 29a in the idlepassage and then combines with a second stream of air coming in throughanother idle air bleed passage 31. This tends to further break up thegasoline particles. This mixture flows downward through idle passage 33to the idle port 32 and mixes with air coming past the almost closedthrottle valve 17; thence, air and fuel are discharged from the lowerportion of the idle port 32 and to idle mixture valve 41 and then outidle port 40. The idle port is slotted so that as the throttle valveopens, it will not only allow more air to come past A the valve, butwill also uncover more of the idle port,

allowing a greater quantity of gasoline and air mixture to flow from theidle system. As the edge of the throttle plate clears the idle portslot, the induced vacuum on the idle system diminishes, and when thepressure differential becomes zero, the idle system ceases to function.The low speed circuit supplies the gasoline for idling and light loadsup to approximately 20 miles per hour; it partially controls supply forlight loads up to 30 miles per hour, since it gradually fades out as thehigh speed circuit cuts in.

It has been thought previously that cold stalling is caused by the icewhich forms on the throttle valve 17 and the idle ports 32 and 40. Ihave discovered, contrary to the prior thinking on the subject, thatcold stalling is caused only partially by the ice which forms on thethrottle valve and idle ports, and that the ice which forms in theinitial idle air bleed section of the idling system, in other words ator near openings 30 and 31, is the main cause of cold stalling. Duringmy experimental work described in the examples, I have observed iceformation in the idle air bleed openings of the carburetor under test.To eliminate ice formation in the initial idle air bleed section of theidle fuel system, I have provided an electrical heater 34 between airbleeds 30 and 31. The heater need not be very large, and in most cases,a to 40 watt heater will be suflicient;however, larger or smallerheaters may be used, if desired. The operation of heater 34 iscontrolled by an electrical circuit, for example, comprising anelectrical energy source 35, engine ignition switch 36 and a bimetallicelement 37. The bi-metal element 37 is preferably attached to thecarburetor wall or body by silver solder, and contact 38 is suitablyinsulated from the carburetor body. When the ignition switch 36 isturned to the on" position, the heater begins to heat the wall areaaround air bleeds 30 and 31. After the car is started and begins towarm-up, the bi-metallic element 37 moves toward the carburetor wall,and breaks the circuit to the heater. In actual operation the electricalcircuit is broken only after the carburetor has picked up enough heatfrom the engine that icing is no longer a problem. Thus, the formationof ice is prevented in the air bleed section of the idle system.Laboratory tests have shown that engine operation is practically normaland very few cold stalls occur when the initial air bleed section of theidle fuel system of the carburetor is locally heated above its icingtemperature. If desired, the bimetallic element 37 can be placed into orin close proximity to the idle air passage. As shown, the switch ismounted on the carburetor and will interrupt the current when thetemperature of the carburetor is such that the temperature in thepassage is above a stalling temperature.

While the present invention has been primarily concerned with the use ofan electrical heater located in the vicinity of the idle air bleedopenings of a carburetor, it is obvious that other means can be providedto accomplish the same result. For example, passage 42 can be locatedalong side of the idle system passages so that exhaust gases or heatedair can be passed through these passages. Engine coolant can be passedthrough the passage if desired provided that a sufficient volume of thecoolant is employed to maintain the adjacent carburetor parts above theicing temperature. The amount of heat exchange fluid passed through thepassages can be controlled with an electrical circuit similar to the onedescribed for the drawing. Or an electrical system can be provided tocontrol a valve which, in turn, will control the amount of coolant orheat exchange material passed through the passages. Alternatively, thevalve can be mechanically linked to the bimetallic strip so that noelectrical system is necessary. Also, instead of using a thermal switch,such as a bimetallic type of unit, to control heating of the idle airbleed section, a thermocouple and One skilled in the art in possessionof this disclosure will understand that the invention is applicable toall those cases in which cold stalling occurs regardless of the natureof the fuel or oxidant which may be employed. Thus, the point of theinvention is in the discovery of the locus at which the lowering oftemperature causes a temporary ice obstruction or restriction of flow ofthe air.

Reasonable variation and modification are possible within the scope ofthe foregoing disclosure, drawings, and the appended claims to theinvention, the essence of which is that an improved method and apparatusfor the operation of an internal combustion engine of the carburetortype have been provided wherein, as described, the initial air bleedsection of the carburetor is heated.

I claim:

1. In an automotive internal combustion engine which when said ignitionswitch is closed.

amplifier, for example, may be used. Neither is the present inventionlimited to the carburetor shown in the drawing. I a

2. A carburetor system as described in claim 1 wherein said heater isconnected to a thermal responsive switch sensing the temperature of saidcarburetor and operative to cut off flow of current whenever thetemperature in said passage is above a predetermined maximum stallingtemperature.

3. An anti-stalling carburetor device for an internal combustion enginecomprising an idle air bleed passage and a heater in heat exchangerelation with the passage.

4. A device according to claim 3 wherein said heater is an electricalheater.

5. An anti-stalling carburetor device comprising in combination an idleair passage formed within the body of said carburetor, and a heatingmedium flow passageway in indirect heat exchange relationship with saididle air passage.

6. A method of operating an air-fuel carburetor subject to cold stallingwhich comprises heating the air in the initial air bleed section of theidle fuel system of said carburetor.

7. A method of preventing cold stalling of an internal combustion enginedue to ice formation in an air-fuel carburetor zone which has an initialair bleed section located in an idle fuel supply zone which comprisesheating the walls of said initial air bleed section.

8. A method according to claim 7 wherein the initial air bleed sectionis heated by passing hot heating medium into heat exchange relationshipwith said section.

9. In a carburetor adapted to produce an air-fuel mixture for aninternal combustion engine, in combination, an idling system comprisinga passageway for conducting fuel through a calibrated restriction intoadmixture with initial bleed air, a bleed air passageway communicatingwith the atmosphere surrounding said carburetor and a locus adjacentsaid calibrated restriction for admitting air into admixture with saidfuel and an indirect heat exchange means for heating at least one wallof the locus at which the initial air bled into the carburetor and thefuel come into contact each with the other.

10. An apparatus according to claim 9 wherein the heating means is anelectrical heater, said heater is operatively connected to a source ofelectrical current, said source of electrical current is controlled by aswitch and there is positioned upon the line of flow of current athermal responsive element adapted to open the circuit to the heaterwhenever the carburetor has reached a temperature above which stallingwill not occur.

References Cited in the file of this patent UNITED STATES PATENTS2,715,520 Boyce Aug. 16, 1955

